Entropy‐Enabled Site Inversion and Defect Activation in Medium‐Entropy Spinels for Near‐Black Infrared Emission
Abstract
ABSTRACT Spinel infrared (IR) coatings are attractive for high‐temperature thermal management but often deliver sub‐black emissivity and suffer thermal drift. Although entropy‐stabilized oxides have been explored, most prior demonstrations remain case‐by‐case without a unifying principle for tailoring infrared radiation. Here, we report a medium‐entropy inverse spinel, where configurational entropy drives partial site inversion and defect formation, coherently tuning both band structure and lattice dynamics. The ceramic achieves near‐blackbody emissivity (∼0.90, 0.78–16 µm) and more than doubles the parent oxide in the 2–8 µm band critical for radiative heat transfer above 1000°C. It remains a single‐phase and higher emissivity after 200 h at 1300°C. The material exhibits low thermal conductivity (0.53 W·m −1 ·K −1 , 800°C), and as a sprayable coating reaches a hemispherical emissivity of ∼0.96 on steel and refractories, increasing furnace temperature by ∼44.3°C. Spectroscopy and density functional theory (DFT) reveal entropy‐driven mixed‐valence states, abundant oxygen vacancies, band gap narrowing (∼0.7 eV), and activation of IR phonons. This work establishes a generalizable strategy, coupling configurational entropy and site inversion, to convert robust spinels into near‐black, durable radiators, offering a scalable platform for energy‐saving coatings in extreme environments.
Article Details
Authors (8)
Ge‐Ting Sun
Key Laboratory of Energy Conservation and Energy Storage Materials of Gansu Province Research Center for Resource Chemistry and Energy Materials State Key Laboratory of Solid Lubrication Lanzhou Institute of Chemical Physics Chinese Academy of Sciences Lanzhou P. R. China
Cheng‐Yu He
Key Laboratory of Energy Conservation and Energy Storage Materials of Gansu Province Research Center for Resource Chemistry and Energy Materials State Key Laboratory of Solid Lubrication Lanzhou Institute of Chemical Physics Chinese Academy of Sciences Lanzhou P. R. China
Bao‐Hua Liu
Key Laboratory of Energy Conservation and Energy Storage Materials of Gansu Province Research Center for Resource Chemistry and Energy Materials State Key Laboratory of Solid Lubrication Lanzhou Institute of Chemical Physics Chinese Academy of Sciences Lanzhou P. R. China
Jun‐Jie Liu
Key Laboratory of Energy Conservation and Energy Storage Materials of Gansu Province Research Center for Resource Chemistry and Energy Materials State Key Laboratory of Solid Lubrication Lanzhou Institute of Chemical Physics Chinese Academy of Sciences Lanzhou P. R. China
Chun Wang
Jun‐Wei Lang
Key Laboratory of Energy Conservation and Energy Storage Materials of Gansu Province Research Center for Resource Chemistry and Energy Materials State Key Laboratory of Solid Lubrication Lanzhou Institute of Chemical Physics Chinese Academy of Sciences Lanzhou P. R. China
Lei Wang
Xiang‐Hu Gao
Key Laboratory of Energy Conservation and Energy Storage Materials of Gansu Province Research Center for Resource Chemistry and Energy Materials State Key Laboratory of Solid Lubrication Lanzhou Institute of Chemical Physics Chinese Academy of Sciences Lanzhou P. R. China